This feature is available on all Goodshuffle Pro Plans.
As the online refund failed, another refund for this payment must be recorded "Offline" (Article). This is to help balance the project and to ensure another online refund attempt does not fail.
In the event an online refund does fail, these funds will be returned to your account and marked as an "Other Payment" in the billing tab of your project. Account owners/administrators are notified of the failure, and the refund will show as "Failed" in the billing tab.
Online refunds can fail for a few reasons. For credit cards, it's possible the card has been changed or canceled since the payment was made. With ACH transactions, the bank account may have been closed. If the reason is known it will be shown in the additional information of the failed refund.